1. Field of the Invention
The present invention relates to an active-matrix light-emitting apparatus. In particular, the present invention relates to an active-matrix display apparatus that performs driving-control of electronic devices, such as EL (electroluminescent) devices and LED (light-emitting diode) devices, that are caused to emit light by a driving current flowing to emitting layers such as organic semiconductor films using thin-film transistors (hereinafter, referred to as TFTs), and relates to a fabrication method therefor.
2. Description of Related Art
Active-matrix light-emitting apparatuses, particularly, the apparatuses used for active-matrix type display apparatuses using current-control light-emitting devices, such as EL devices and LED devices, have been proposed. The light-emitting devices used in display apparatuses of this type emit light by themselves. Therefore, unlike liquid crystal display apparatuses, they have advantages in such aspects in that they do not require a backlight and that they are less dependent on viewing angles.
FIG. 1 is a schematic view of a circuit configuration in an active-matrix display apparatus using organic thin-film EL devices of a charge-injection type as current-control light-emitting devices. In the active-matrix display apparatus 1 shown in this figure, switching circuits 50 and light-emitting devices 40 are individually formed for pixels 7, in which the pixels 7 are formed in a matrix by a plurality of scanning lines xe2x80x9cgatexe2x80x9d and a plurality of data lines xe2x80x9csigxe2x80x9d, switching circuits 50 are fed with scanning signals through the scanning lines xe2x80x9cgatexe2x80x9d, and the light-emitting devices 40 emit light in response to image signals fed from data lines xe2x80x9csigxe2x80x9d through the switching circuits 50. In the illustrated example, each of the switching circuits 50 is formed of a first TFT 20 in which scanning signals are fed to its gate electrode through the scanning line xe2x80x9cgatexe2x80x9d, a capacitor xe2x80x9ccapxe2x80x9d for storing image signals fed from the data line xe2x80x9csigxe2x80x9d through the first TFT 20, and a second TFT 30 in which the image signals stored in the capacitor xe2x80x9ccapxe2x80x9d are fed to its gate electrode. When the second TFT 30 is turned on, a driving current flows from a common feeder line xe2x80x9ccomxe2x80x9d into the light-emitting device 40 to cause the device to emit light, and the light-emitting state is maintained according to the capacitor xe2x80x9ccapxe2x80x9d.
FIGS. 2 and 3 are plan views of a portion of the pixels shown in FIG. 1. In FIG. 2, conductive films forming elements such as the scanning lines xe2x80x9cgatexe2x80x9d and capacitor lines xe2x80x9ccsxe2x80x9d are indicated by lines slanting up to the right; elements such as conductive films forming the data lines xe2x80x9csigxe2x80x9d and the common feed lines xe2x80x9ccomxe2x80x9d are indicated by lines slanting down to the right. In FIG. 3, regions in which the light-emitting layers 43 composing the light-emitting devices 40 are formed are indicated by lines slanting down to the right. For reference, in the illustrated example, an insulation film xe2x80x9cinxe2x80x9d defining the regions in which light-emitting layers 43 are formed is arranged in a border region in which the data line xe2x80x9csigxe2x80x9d and the common feed line xe2x80x9ccomxe2x80x9d extend in a border region between the individual pixels 7, therefore, the regions in which the insulation films xe2x80x9cinxe2x80x9d are formed are indicated by the lines slanting up to the right. In addition, in FIGS. 2 and 3, regions in which semiconductor films forming the first TFTs 20 and the TFTs 30 are formed are indicated by bold lines; regions in which pixel electrodes 41 are formed are indicated by bold dotted lines. In addition, respective cross sections along the lines A-Axe2x80x2, B-Bxe2x80x2, and C-Cxe2x80x2 in FIGS. 2 and 3 are shown in FIGS. 12, 13, and 14.
In these figures, the first TFT 20 has a structure in which a gate electrode is formed as a part of the scanning line xe2x80x9cgatexe2x80x9d, and the data line xe2x80x9csigxe2x80x9d and a storage electrode 22 are respectively formed in a source region and a drain region through a contact hole of an interlayer insulation film 51. The storage electrode 22 extends toward the region in which the second TFT 30 is formed, and a gate electrode 31 of the second TFT 30 is electrically connected through the contact hole in the interlayer insulation film 51 in the foregoing extension portion. The capacitor line xe2x80x9ccsxe2x80x9d is formed at a side portion of the scanning line xe2x80x9cgatexe2x80x9d, and the capacitor line xe2x80x9ccsxe2x80x9d is commonly positioned for the drain region of the first TFT 20 and the storage electrode 22 via the first interlayer insulation film 51 and a gate insulation film 55 to form the capacitor xe2x80x9ccapxe2x80x9d. A junction electrode 35 is electrically connected to either one of the drain region and the source region of the first TFT 30 through the contact hole in the first interlayer insulation film 51, and a pixel electrode 41 is electrically connected to the junction electrode 35 through a contact hole in a second interlayer insulation film 52. To the other of the drain region and the source region, the common feeder line xe2x80x9ccomxe2x80x9d is electrically connected through the contact hole in the first interlayer insulation film 51.
The pixel electrode 41 is formed independently for each pixel 7. On an upper side of this pixel electrode 41, a light-emitting layer 43 composing the light-emitting devices 40 and an opposing electrode xe2x80x9copxe2x80x9d are overlaid in this order.
In the illustrated example, the insulation film xe2x80x9cinxe2x80x9d is formed in a region in which the data line xe2x80x9csigxe2x80x9d and the common feeder line xe2x80x9ccomxe2x80x9d extend, and the insulation film xe2x80x9cinxe2x80x9d insulates the light-emitting layers 43 of the light-emitting devices 40 of two pixels 7 which are arranged on both sides of the data line xe2x80x9csigxe2x80x9d and the common feeder line xe2x80x9ccomxe2x80x9d. However, the insulation film xe2x80x9cinxe2x80x9d is not formed between the pixels 7 arranged along the data line xe2x80x9csigxe2x80x9d and the common feeder line xe2x80x9ccomxe2x80x9d. In this direction, the light-emitting layers 43 of the light-emitting device 40 are formed in stripes so as to overlap a plurality of the pixels 7. In this arrangement also, the first TFTs 20 of the individual pixels 7 turn on/off with a predetermined timing in response to scanning signals fed from the scanning lines xe2x80x9cgatexe2x80x9d, therefore, predetermined image signals are written to the individual pixels 7 from the data lines xe2x80x9csigxe2x80x9d, and a current flows to the light-emitting layers formed in the border lines between the pixels.
In conventional active-matrix display apparatuses, although predetermined image signals from the data lines xe2x80x9csigxe2x80x9d can be written to the individual pixels 7, since the light-emitting devices 40 (light-emitting layers 43) have electrical conductivity, a current also flows to between pixels (the border regions between the pixels) arranged along the data lines xe2x80x9csigxe2x80x9d and the common feeder lines xe2x80x9ccomxe2x80x9d, increasing the probability of occurrence of the so-called crosstalk. In addition, if charge injection layers such as hole injection layers, electron injection layers, and the like are formed in the light-emitting devices 40 in addition to the light-emitting layers for improving the light-emitting characteristics, the resistance of the charge injection layer is smaller than that of the light-emitting layer, and the difference in the resistance might further increase the probability of occurrence of crosstalk between the pixels arranged along the data lines xe2x80x9csigxe2x80x9d and the common feeder line xe2x80x9ccomxe2x80x9d.
In view of the above problems, objects of the present invention are to provide an active-matrix light-emitting apparatus and a fabrication method therefor, the active-matrix light-emitting apparatus being such that it has a plurality of pixels and is arranged so as to avoid crosstalk in the vicinity between the pixels, and to provide display of improved quality.
To solve the above problems, the present invention provides an active-matrix display apparatus that has pixel electrodes formed in individual pixels in a matrix by a plurality of scanning lines and a plurality of data lines, light-emitting layers overlying the pixel electrodes, and opposing electrodes formed on the light-emitting layers. The light-emitting devices composed of the light-emitting layers emit light in response to image signals fed from the data lines via a switching circuit. The apparatus includes insulation films between the pixel electrodes and the light-emitting devices, in each of which upper portions at side face sections protrude from a lower portion in the border regions.
In the present invention, step-cutting insulation films, each having the upper portions specifically structured as described above, in interlayer sections of the pixel electrodes and the light-emitting layers, that is, in a lower side of the light-emitting devices, are arranged in border regions in which the light-emitting layers are individually arranged on an upper portion so as to overlap in the border regions of the pixels. Therefore, step-cutting is produced by the upper portions protruding toward the sides of the insulation films in the light-emitting layers formed over the foregoing insulation films. For this reason, even light-emitting layers formed individually so as to overlap interpixel sections can be insulated in the interpixel sections. Even when complete step-cutting does not occur in the light-emitting layers, but when very thin sections are therein formed, resistance in these sections is significantly high. Therefore, even in an active-matrix display apparatus in which the light-emitting layers are formed individually so as to overlap a plurality of pixels, crosstalk between these pixels does not occur and display quality is improved.
It is preferable that charge injection layers be arranged for injecting holes or electrons to the light-emitting layers at a lower side of the light-emitting layers, by which the present invention is made more advantageous. In this case, the film thickness of the insulation films is preferably greater than that of the charge injection layers. Since the charge injection layers in the light-emitting devices have a resistance less than that of the light-emitting layers in the light-emitting devices, crosstalk tends to occur frequently in interpixel sections in which the light-emitting devices are formed so as to overlap. However, the above arrangement for the relation between the thicknesses of the charge injection layers and insulation films produces the step cutting 43c in the charge injection layers so that the interpixel sections are substantially insulated and crosstalk is avoided. In this way, in the present invention, when the film thickness of the insulation films is arranged to be greater than that of the light-emitting layers, avoidance of crosstalk can be ensured.
In the present invention, interpixel border regions are, for example, border regions between the pixels arranged along the data lines or the scanning lines. It is preferable that the insulation films structured as described above be formed at least in the border regions.
The interpixel border regions may also be border regions between the pixels arranged along the data lines and border regions between the pixels arranged along the scanning lines. In this case, the aforementioned insulation films are to be formed in any of the border regions. In such an arrangement, even when ink (light-emitting devices in a liquefied state) overflows from the pixels in any direction in forming the light-emitting devices in a method such as an ink-jet method, the light-emitting devices produce the step cutting in upper portions of the insulation films in the border regions between the pixels, insulating the interpixel sections.
In the present invention, it is preferable that side face sections of the insulation films be, for example, tapered so that upper portions of the side face sections protrude from a lower portion. Alternatively, the insulation films may be shaped so as to have a two-step structure including upper portions of side face sections formed to be wider than a lower portion.
In the present invention, there may be a case in which the switching circuit includes, for example, the first thin-film transistor in which the scanning signals are fed to its gate electrode and the second thin-film transistor in which its gate electrode is connected to the data line through the first thin-film transistor. In this case, the second thin-film transistor and the light-emitting device are connected in series between each of common feeder lines and each of the opposing electrodes, the common feeder lines being arranged separately from the data lines and the scanning lines.
The present invention also provides a fabrication method for an active-matrix display apparatus having pixel electrodes formed in pixels arranged in a matrix by a plurality of scanning lines and a plurality of data lines, light-emitting layers overlying the pixel electrodes, and opposing electrodes formed on the light-emitting devices, wherein the light-emitting layers emit light in response to image signals fed from the data lines via a switching circuit. The method includes a step of forming electrodes; a step of forming insulation films in regions corresponding to border portions between a plurality of the pixels, the individual insulation films having upper portions of side faces protruding from a lower portion; and a step of arranging materials of the light-emitting layers from an upper portion of the insulation films so as to overlap the regions corresponding to the border regions between the plurality of pixels.
The active-matrix light-emitting apparatus of the present invention, which may be an apparatus that controls light emitted by means of active-matrix circuits through light-emitting devices, may be used as a display apparatus and as other light control apparatuses.